K8T890 issue - 3x512 = 1gb?

[Cardinal Fang]

ABIT AX8, K8T890, latest BIOS. 2 sticks of 512mb PC3200. Dual channel/single channel works as it should depending on if I use the right pair of slots. When I add a third 512mb stick it of course goes back to single channel, but doesn't get counted by the BIOS - 3 sticks still shows 1gb at the POST screen. Any combo of two of the 3 work fine in any of the 4 slots, as they should. The weird part is, cpu-z detects all 3 sticks, reads the SPD correctly from all 3 sticks, and shows the total memory as 1536mb, but BIOS and the OS only show 1gb.

http://i35.tinypic.com/28ip9xw.jpg

Is this a known issue with the K8T890?

[Thrax]

Try turning the /PAE switch off in your boot.ini

[Cardinal Fang]

How would that affect only 1gb being counted at the POST screen?

[Thrax]

Oops, didn't catch the POST bit.

Do you have a memory remap option in the BIOS? Allows for mapping of memory in/out of the memory space. Could be that's screwing with things.

Alternatively, that motherboard could have a memory bank limit. Three sticks of double-sided DDR is six banks, which some older (or poorly-implemented) chipsets throw a fit over.

Lastly, and most obscurely, does the motherboard <i>demand</i> matched pairs?

[Cardinal Fang]

The original bios supported 4 double bank modules for a total of 4gb, updated bios supports 8gb. I don't think they actually changed anything, but 2gb modules weren't available when the board was new. There's a chart showing valid configs, but it only shows various combos of 1, 2, and 4 sticks. Nothing specifically says 3 won't work.